How does exercise affect cellular respiration?

​This is an easy classroom activity.  Each student will need a straw, 2 test tubes, and bromothymol blue.  Each group of two students can share a stopwatch.

Ask students to predict if exercise will affect cellular respiration, and, if so, in what way?

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​PROCEDURE

• Set up tests tubes with 10 mL of bromothymol blue in each.  
• The activity is performed in two rounds.  Time both rounds.  In the first round, blow through a straw into the bottom of the first test tube.  Be careful not to inhale.  Time how long it takes for the color of the bromothymol blue to change.  Note the BEFORE EXERCISE time in a data collection table.
• In the second round, exercise vigorously (jog, jumping jacks, burpees, etc) in place for one minute.  Use the same straw to blow into the bottom of the second test tube.  Be careful not to inhale.  Note the AFTER EXERCISE time on your data collection table.

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A class with 15-30 students can display their data on a graph to analyze the trends.  "Typical" data can be provided for smaller classes so that they can graph a larger quantity of data points.  Examples of "typical" before and after exercise times  are:  

​Before Exercise (5:04, 4:09, and 4:14); After Exercise (2:03, 2:01, and 1:56).

Students can transfer their data to a graph like the one below.

After the class has completed the activity, ask students how exercising affected the time it took for the bromothymol blue to change color.  Was their prediction correct?  Discuss the bodily process the produces CO2 (cellular respiration). 

This quick lab is a great addition to a Cellular Energy Unit.  An organized lab form for this activity can be found here.